1. Field of the Invention
This invention relates to a printer or printer system using the Java language to control rasterizing an image and to control printing.
2. Description of the Background
The Internet is undergoing explosive growth and many new technologies are being developed to keep up with this growth. Previously, in order to develop applications quickly, application developers sought to use specialized cross-platform application development techniques which create applications for multiple hardware and software platforms. For example, operating systems (i.e. Solaris, Windows 95, Windows 3.x, OS/2 and Unix) create applications and executable files differently and have been implemented on various processor types (Intel processors, 680.times.0, Power PCs, and Sun SPARCS). To develop applications for all permutations of operating systems and hardware is difficult and extends the product development cycle. To make cross-platform development faster and easier, Sun Microsystems developed a language called Java which is object-oriented but simple. Java is described in Java in a Nutshell: A Desktop Quick Reference for Java Programmers by David Flannagan, published by O'Reilly & Associates, Inc., as well as in the Sun Series of books published by Prentice Hall Books entitled Core Java, Instant Java, Java by Example, and Just Java by Cornell, Pew, Jackson and Van Der Linden, respectively, which are incorporated herein by reference. One of Java's advantages is that it is a portable language which is independent of operating systems and hardware architectures. Further, applications developed using Java are adaptable or extendable using Java's ability to download new classes dynamically and to add the downloaded classes to an existing class hierarchy. Java also provides the advantages of distribution, language interpretation, security, high performance and a multi-threaded implementation.
Java enables applications to be written using an extensible set of objects, with each set of objects being defined in a separate group of objects called a package. The core set of objects for Java are defined in the java.lang package and describe the most central characteristics of the Java language. One of Java's advantages is that the character type that Java uses is the Unicode standard which allows English and Asian characters to be represented consistently and together in applications or documents generated using Java.
Other languages have been used to represent the layout of documents as they appear on printers. PostScript by Adobe is an extendable page-layout language which supports text and graphics on the same page. Some aspects of PostScript are described in PostScript by Example by Henry McGilton and Mary Campione, published by Addison-Wesley Publishing Company, the contents of which are incorporated herein by reference. PostScript uses stacks and dictionaries to extend the language. Some PostScript printers also have been equipped with non-volatile memories which are used to store configuration information for the printers. However, PostScript's lack of strong security features has enabled malicious users of the printer to update the parameters stored in the non-volatile memory, thereby disturbing the printer's use in network environments.
Other printer languages, such as PCL by Hewlett-Packard, have evolved from uni-directional, dot-matrix line printers and therefore lack many of the operators needed to control the placement of images on a page. PCL also lacks modularity. The macros defined by PCL use globally scoped variables that can affect the performance of other macros defined by the language.
Currently, all of the applications that print from host systems have to convert their internal document format to PostScript or PCL and then download the document to the printer using a printer driver designed to work with the specifics of the connected printer. Since there is a wide variety of printers that can be used, each with a slightly different set of features and/or bugs, a large number of printer drivers have traditionally been shipped with applications, even though end-users actually only need the printer drivers for their specific printers. Furthermore, using conventional printing techniques, an inadvertent change in the printer driver used could cause the printer to print out the commands which describe how a page is to be laid out rather than interpreting the commands and rendering a resulting image. Further, for printers which support downloadable fonts, downloading of fonts often has been restricted to downloading to the printer's RAM, ROM font cartridge or attached hard disk.
This model of application and printer driver interaction has created an increase in work performed by end-users because of the inflexibility and limited communication capability of the printer when communicating with the application.